jbd2: Add sanity check for attempts to start handle during umount

An attempt to modify the file system during the call to
jbd2_destroy_journal() can lead to a system lockup.  So add some
checking to make it much more obvious when this happens to and to
determine where the offending code is located.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index f3479d6e0a83..6bf0a242613e 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -156,6 +156,7 @@ alloc_transaction:
          */
 repeat:
         read_lock(&journal->j_state_lock);
+        BUG_ON(journal->j_flags & JBD2_UNMOUNT);
         if (is_journal_aborted(journal) ||
             (journal->j_errno != 0 && !(journal->j_flags & JBD2_ACK_ERR))) {
                 read_unlock(&journal->j_state_lock);